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To: cs551@merlot.usc.edu
Subject: Re: SHA1 function returning incorrect hash value
Date: Fri, 14 Nov 2008 12:25:48 -0800
From: Bill Cheng <william@bourbon.usc.edu>

Someone wrote:

  > So is the following correct to check the SHA1 of a file itself?:
  > 
  > cat blondie1.mp3 | openssl sha1
  > 
  > The reason I ask is that my SHA1 output for blondie1.mp3 matches the output
  > from the above, but it doesn't match the output in the spec, so I just want
  > to double check.

The FileSize also did not match because the file, "blondie1.mp3",
is actually different!  (I think "blondie1.mp3" is not even a
MP3 file.)  I've updated the SHA1 and FileSize values in the spec.
Sorry about the confusion.
--
Bill Cheng // bill.cheng@usc.edu <URL:http://merlot.usc.edu/william/usc/>





  On Mon, Nov 10, 2008 at 9:47 PM, Bill Cheng <william@bourbon.usc.edu> wrote:
  > Someone wrote:
  >
  >  > Is there any similar utility like the one we had for warmup1 (
  >  > ~csci551b/bin/filemd5 [-o offset] [file]) to check the SHA1 value ?
  >
  > You can run "openssl sha1 [file]".
  >
  > If you have a short ASCII string, you can do:
  >
  >    echo -n "YOURSTRING" | openssl sha1
  > --
  > Bill Cheng // bill.cheng@usc.edu <URL:http://merlot.usc.edu/william/usc/>
  >
  >
  >
  >
  >   On Mon, Nov 10, 2008 at 7:45 PM, Bill Cheng <william@bourbon.usc.edu>
  > wrote:
  >
  >  > Someone wrote:
  >  >
  >  >  > When I used SHA1() / MD5 function to calculate hash value of a string
  > I
  >  > do
  >  >  > get incorrect value.
  >  >
  >  > Could you give an example?
  >  >
  >  >  > But if I used *SHA1_Init()*, *SHA1_Update()* and *SHA1_Final()* ,
  >  >  > collectively I do get correct hash value ?
  >  >  > Same is the case with MD5.
  >  >  >
  >  >  > What could be the reason for this ?
  >  >
  >  > Bugs?!
  >  >
  >  >  > Or its safe to use *SHA1_Init()*, *
  >  >  > SHA1_Update()* and *SHA1_Final()* functions always ?
  >  >
  >  > They are equivalent.  For example, in GetUOID(), we call
  >  > SHA1() directly.  It would be an overkill to use
  >  > SHA1_Init(), SHA1_Update(), and SHA1_Final().
  >  > --
  >  > Bill Cheng // bill.cheng@usc.edu <URL:http://merlot.usc.edu/william/usc/>